Optimization of the experimental resolution for small-angle scattering

Small angle neutron scattering (SANS) instruments typically cover a q (scattering vector) range from 0.001 to 0.6 Å−1. This range in q is achieved through a combination of cold neutrons (λ>4 Å) and a highly collimated beam. However, as a direct result of the unavailability of a cold source at the Canadian Neutron Beam Centre (CNBC), we have resorted to adapting a triple-axis spectrometer to perform SANS measurements. This is achieved through the use of multiple converging incident beams which enhance the neutron flux on the sample by a factor of 20, compared to a single beam of the same spot size. Furthermore, smearing effects due to vertical divergence from the slit geometry are reduced through the use of horizontal Soller collimators. As a result, this modified triple-axis spectrometer enables SANS measurements to a minimum q value (qmin) of ∼0.006 Å−1. Data obtained from the modified triple-axis spectrometer are in good agreement with those data from the 30 m NG3-SANS instrument located at the National Institute of Standards and Technology (Gaithersburg, MD, USA).

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“…1,2 To minimize peak asymmetry, as shown in Fig. 4, the dimension of q y 2 should approach that of q x 2 .…”

Section: B the Resolution Functionmentioning

confidence: 99%

Adapting a triple-axis spectrometer for small angle neutron scattering measurements

Nieh

Yamani

Kučerka

et al. 2008

Review of Scientific Instruments

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“…For the SANS instrument in this normal configuration the resolution is AQ, = 0.081 nm-1. Using a pinhole of size 0.7 mm before the sample and a shorter source-sample distance, the data (also shown in Figure 4) now have a resolution AQ, = 0.112 nm-1 (with the source term dominant in the resolution expression [9]). …”

Section: Measurementsmentioning

confidence: 99%

Low-resolution small-angle scattering using neutron focusing optics

et al. 1993

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Experiments at low values of scattering vector require tight collimation in the primary beam, as well as the ability to make measurements with good spatial resolution on the detector. Because neutron sources are not as intense as X-ray sources, large source and sample areas are used, and long instruments are necessary for adequate resolution. Increased count rates may be obtained using collimated beams which converge to a point on the detector. Further increases may be obtained with converging guides in the form of a focusing lens to increase the effective flux. Narrow guides enable the spectrometer dimensions to collapse for the same resolution. The critical angle of the fibers forming the focusing lens dominates the resolution, and such an instrument is useful only for low resolution measurements. However the greatly reduced length is only valuable if there is a high resolution detector to match the dimensions of the guide.

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“…The first aperture becomes the effective source position and the sample is placed immediately beyond the second aperture. The instrumental optimization conditions for most small-angle scattering experiments have been given before (Schmatz, Springer, Schelten & Ibel, 1974;Mildner & Carpenter, 1984). These require that the distances LI, between the effective source and the sample, and L2, between the sample and the detector, are the same, and that the size of the effective source R 1 and the sample R 2 are related to the detector-element size, X 3 by Y3, by…”

Section: Focusing Spectrometermentioning

confidence: 99%

“…That is, at small angles. In papers I and II (Mildner & Carpenter, 1984, 1987, we have written the scattering vector in terms of quantities T,(r), which depend on the ratio of transverse to longitudinal dimensions up to the second power. Paper I gives the average values of the scattering vector and its magnitude in terms of these quantities.…”

Section: Appendixmentioning

confidence: 99%

Neutron focusing optics for low-resolution small-angle scattering

Mildner¹

1994

J Appl Cryst

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Small-angle neutron scattering instruments use large source and sample areas with long flight paths to obtain the necessary resolution. Increased count rates may be obtained using collimators that converge to a point on the detector. Further increases may be obtained by converging guides in the form of a focusing lens. A low-resolution small-angle scattering instrument that uses converging capillary fibers as a focusing lens is proposed. Such a device requires the use of a detector that has a fine spatial resolution, perhaps less than 0.1 mm. Expressions are derived for the resolution and the intensity optimized for such an instrument. The relationship is determined between the guide dimensions, the focal length and the critical angle of the internal coating of the individual fiber channels. The critical angle of the focusing lens dominates the resolution, and such an instrument is useful only for low-resolution measurements. However, the greatly reduced length is only valuable if there is a high-resolution detector to match the dimensions of the guide. Despite its low resolution, such an instrument might eventually be useful for survey or characterization measurements.

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Optimization of the experimental resolution for small-angle scattering

Cited by 99 publications

References 4 publications

Adapting a triple-axis spectrometer for small angle neutron scattering measurements

Adapting a triple-axis spectrometer for small angle neutron scattering measurements

Low-resolution small-angle scattering using neutron focusing optics

Neutron focusing optics for low-resolution small-angle scattering

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